A) Field of the Invention
This invention relates to a method and apparatus for performing a detailed analysis of digital pictures and, in particular, pictures taken of an effluent such as smoke or dust to determine the opacity of the effluent.
B) Background of Invention
The existence of pollution creates many general health concerns and the government has enacted legislation to regulate pollution levels. In particular, the government has sought to control the amounts of particulate matter in the air. Particulate matter generally refers to particles in the air that are invisible individually and visible as smoke en masse.
In order to control the distribution of these particulate matter, the Environmental Protection Agency promulgated regulations which are directed to anyone who produces smoke. These regulations require that smoke emitted into the atmosphere not exceed certain levels that have been empirically determined to be acceptable for a given operation. Under the regulations, any individual or company that produces smoke must demonstrate that the smoke levels emitted are within the established parameters to obtain a permit with their local authority.
In order to determine the amount of smoke that is output into the atmosphere, a smoke plume is analyzed to determine the opacity of the smoke plume. Opacity is generally considered to be a value of the density of the smoke.
Some devices exist that are installed within the smoke stack to measure the opacity of the smoke plumes. Referred to as Continuous Opacity Monitors (xe2x80x9cCOMxe2x80x9d), these devices essentially utilize a light source and a photo cell detector. The light source and photo cell detector are placed at opposite walls within the smoke stack with the smoke plume in between the two. The light source directs its light toward the detector through the smoke plume. The photo cell detector measures the amount of light that passes through the smoke plume and calculates the opacity based on that percentage. The COMs, however, require difficult maintenance and may not accurately measure opacity depending on the location of light source detector in the stack and characteristics of the effluent such as water content. COMs are also expensive to replace if they break down.
Another method of measuring opacity levels of smoke plumes is for a human to visually observe the plume and estimate the opacity. The government issued a set of regulations, called Method 9 under the Environment Protection Agency Title 5, which established guidelines for the visual determination of opacity emissions from stationary resources.
Under Method 9, a qualified observer views the plume from a requisite distance away from the plume at set intervals of time. The observer then makes a subjective estimate of the percentage of opacity of the plume based on his observations and training.
In order to be an observer qualified to make opacity readings under Method 9, a person must attend a series of classes commonly known as xe2x80x9csmoke schoolxe2x80x9d. In smoke school, the observer is taught the statutory guidelines and exposed to various smoke plumes to evaluate. Based on this experience, the observer becomes trained in identifying opacity levels of smoke plumes. After passing a test of these abilities, a person then qualifies to measure the opacity of smoke plumes.
Smoke plumes can differ in volume, size and color. Each case requires a different analysis regarding the opacity of the effluent. In addition, since these measurements usually occur outdoors, atmospheric conditions also affect the analysis. While a person who has had substantial experience with judging opacity for all different conditions can account for variations in the ambient conditions when making the opacity estimation, the fidelity of the results from a Method 9 visual test can be quite low since they are ultimately based on a subjection evaluation. Opacity judgements are subject to variation of human observers which allow for inconsistencies in measurements. Consequently, it would be advantageous to have a system which offered a more objective and more consistent estimation as to the opacity of the plumes.
Another disadvantage of the human visual observation technique under Method 9 is that once a observation is performed by an observer, there is no ability to repeat the estimation done by that observer. Since the plumes are not fixed in time and each observation can be made only at that specific time, the results of a visual estimation are uncheckable and unrepeatable. Accordingly, it would be advantageous to have a system whereby estimations of opacity can be checked and repeated by the same methods over any period of time.
The current invention involves a computer analysis of digital pictures taken of effluents, such as smoke plumes or dust clouds, to be able to measure opacity levels of the effluent. For smoke plumes, pictures of the plumes to be analyzed are taken and saved as image files. Each picture can be taken in conformance with the regulations established by Method 9 or any other regulatory statutes that are applicable to visual observations to estimate opacity. Each image file is then analyzed to determine the opacity of the smoke plume or dust cloud.
For each picture, the smoke must be isolated in the picture. The background to either side of the smoke is used to determine a standard against which to measure the opacity of the plume. In isolating the smoke in the picture, any artifacts must be removed in the picture. Artifacts are data in the picture file that are not relevant to the analysis. After these artifacts are removed, other phenomena different from the background of the picture must be eliminated. After these filtering processes are completed, the opacity calculation of the smoke plume can be performed by statistically analyzing the data for each pixel that corresponds to the smoke plume.
In accordance with one embodiment of the invention, a method for evaluating a picture of an effluent to determine the opacity of the effluent, comprises the steps of identifying pixels in the picture that pertain to the effluent; deriving data for the pixels in the picture; and analyzing the data for the pixels that pertain to the effluent to determine the opacity of the effluent.
In accordance with another aspect of this embodiment of the invention, the method further comprises the step of obtaining the picture of the effluent to be analyzed.
In accordance with another aspect of this embodiment of the invention, the obtaining step includes the step of taking pictures with a digital camera.
In accordance with another aspect of this embodiment of the invention, the obtaining step includes the step of scanning a picture with a digital scanner.
In accordance with another aspect of this embodiment of the invention, the picture is converted into a graphics file format.
In accordance with another aspect of this embodiment of the invention, the graphics file format is an JPEG file format.
In accordance with another aspect of this embodiment of the invention, the picture has at least a resolution of 800xc3x97600 pixels.
In accordance with another aspect of this embodiment of the invention, the effluent is a smoke plume.
In accordance with another aspect of this embodiment of the invention, the effluent is a dust cloud.
In accordance with another aspect of this embodiment of the invention, the identifying step includes the step of removing artifacts from the picture.
In accordance with another aspect of this embodiment of the invention, the method further comprises the step of selecting a section of the effluent to be analyzed; wherein the identifying and analyzing steps are performed only for the pixels that are included in the selected section.
In accordance with another aspect of this embodiment of the invention, the selected section of the effluent to be analyzed conforms with statutory guidelines governing the selection of a smoke plume to analyze for opacity.
In accordance with another aspect of this embodiment of the invention, the identifying step includes the step of normalizing the data for the pixels.
In accordance with another aspect of this embodiment of the invention, the data comprises color information of the pixels.
In accordance with another aspect of this embodiment of the invention, the data is represented by values in a RGB color space.
In accordance with another aspect of this embodiment of the invention, the color information is represented by values in a HSL color space.
In accordance with another aspect of this embodiment of the invention, the analyzing step comprises the step of performing a principle components analysis on the color information of the pixels.
In accordance with another aspect of this embodiment of the invention, the analyzing step comprises the step of calculating the first principle component of the data of the pixels; and determining the opacity of each pixel pertaining to the cloud by the relationship of each pixel""s data to the first principle component.
In accordance with another aspect of this embodiment of the invention, a single opacity value is calculated for the cloud based on the opacity values of the pixels pertaining to the cloud.
In accordance with another embodiment of the invention, an apparatus for evaluating a picture of an effluent to determine the opacity of the effluent comprises a pixel classifier to define pixels of the picture and determine which pixels pertain to the effluent; the pixels having data characterizing the pixels; and a pixel analyzer to process the data for each pixel and calculate the opacity of each the pixel.
In accordance with another aspect of this embodiment of the invention, the pixel analyzer performs a principle components analysis of the data for the pixels to determine the opacity of each pixel pertaining to the effluent.
In accordance with another aspect of this embodiment of the invention, a single opacity value is calculated for the effluent in the picture based on the opacity values of the pixels pertaining to the effluent.
In accordance with another aspect of this embodiment of the invention, the pixel classifier removes artifacts from the picture and normalizes the data for the pixels.
In accordance with another aspect of this embodiment of the invention, the data comprises color information in a color space.
In accordance with another aspect of this embodiment of the invention, the color space is a RGB color space.
In accordance with another aspect of this embodiment of the invention, the pixel classifier and pixel analyzer operate only on a selected portion of the picture.
In accordance with another aspect of this embodiment of the invention, the pixel classifier and pixel analyzer operate on a plurality of pictures; the plurality of pictures depicting the effluent cloud to be analyzed at different times.
In accordance with another aspect of this embodiment of the invention, a single opacity value is calculated for the effluent in each picture based on the opacity values of the pixels pertaining to the effluent in each picture.
In accordance with another aspect of this embodiment of the invention, a total opacity value is calculated for the effluent based on the single opacity values for the effluent in each picture.
In accordance with another embodiment of the invention, a method for reporting the opacity of an effluent comprises the steps of defining pixels of a picture of the pixels of the cloud; calculating the opacity of the pixels of the cloud; grouping the pixels into different groups; the groups corresponding to a different range of opacity values; assigning each group to a different color; and replacing each pixel of the cloud in the picture with colored pixels corresponding to the color assigned to each group.
In accordance with another aspect of this embodiment of the invention, a method wherein the range of opacity values comprise five percentiles.
In accordance with another aspect of this embodiment of the invention, a method wherein the range of opacity values comprise twenty-five percentiles.